Snow sports such as skiing, sledding and the like are enjoying an ever increasing popularity. This has resulted in an increase in business of winter sports facilities as well as an increased demand for snow covered areas for such facilities. Natural snow is often unpredictably available and frequently in short supply. Increasingly, winter sports facilities are turning to the use of artificial snow-making machinery in order to supplement naturally occurring snow and to extend the sports season. Even in areas where high volumes of naturally occurring snow are present, greater use is being made of artificial snow-making machinery because large numbers of skiers and the like tend to erode snow from slopes at a rate greater than it can be replaced by natural falls.
It has also been found that in many instances artificially made snow is superior to natural snow in terms of wear and groomability. Natural snow tends to be very fine grained and to compact into a solid mass, whereas artificial snow is generally coarser grained material which does not compact but rather allows for drainage of melt-water therethrough and which may be readily groomed by appropriate machinery to restore the natural loft thereto.
For these reasons, artificial snow-making machinery is becoming a standard operational item for skiing, sledding and tobogganing facilities. In general artificial snow is manufactured by directing a stream of moisture bearing air into a freezing or near freezing atmosphere. The earliest snow-making equipment comprised nothing more than a spray nozzle projecting a stream of compressed air and water into the atmosphere. A combination of cold atmospheric conditions and expansive cooling of the air froze the water spray into snow particles. Such equipment is simple in design and easy to operate however its performance is less than adequate. Snow made by the compressed air gun method tends to be very fine grained and prone to compact into an ice-like mass not amenable to grooming or drainage of melt-water; furthermore, such snow does not wear well.
In addition to poor snow quality, the air gun technology is limited by its relative energy inefficiency. Large amounts of compressed air are needed to manufacture snow by this method and such volumes of air are expensive to produce. A typical compressed air gun may consume 500 to 1,000 CFM of air. A general rule of thumb is that it takes approximately 100 horsepower to produce 300 CFM of compressed air; accordingly, it will be appreciated that a typical compressed air gun consumes over 200 horsepower in its operation, necessitating large compressor-motor combinations.
A more recent approach toward the manufacture of artificial snow involves the use of a large fan or blower in conjunction with a water spray. The blower produces a relatively high volume flow of air at pressures only slightly above atmospheric. A spray of water is injected into the stream of air and typically a spray of ice crystal nuclei are also injected so as to seed the moisture laden stream to produce the snow. Such equipment is generally capable of producing high volumes of snow at costs less than those associated with operation of a compressed air gun. While such blower-type equipment is superior in terms of efficiency, problems of control are more critical. For example, proper control of the relative volume of water and air must be maintained. If the amount of water is too low, the volume of snow produced by the machine and hence its efficiency will fall. If the volume of water is too high, not all of the water will be converted to snow and hence the machine will essentially produce rain thereby wetting the previously produced snow and rendering it unusable. The proper volumes of water and air required for most efficient operation will vary as atmospheric conditions vary thereby necessitating frequent adjustment of such blower-type equipment.
Many approaches have been developed to combining water and air in blower-type snow-making equipment in an attempt to secure a wide latitude of operational parameters so as to produce the highest volume of snow at the lowest cost. Additionally, it is desirable that such equipment also produce a high quality of snow.
High quality snow generally may be characterized as having a coarse granular structure which is not prone to compaction so as to allow for a ready draining of melt-water therethrough and so as to provide for easy grooming to restore the loft thereof.
One early approach to the fabrication of blower-type snow-making equipment is represented by U.S. Pat. No. 3,979,061 in which a plurality of nozzles are disposed externally of a stream of air so as to spray high pressure water into that stream. Nucleation is accomplished by impinging a high pressure, low volume stream of air into the water stream so as to initiate freezing proximate its point of introduction. This apparatus was hard to keep in adjustment and water droplets tended to fall out of the air stream prior to crystalization so as to form ice patches and wet regions on previously deposited snow. Another early approach is detailed in U.S. Pat. No. 3,948,442 which teaches the use of a high volume air blower having a pulsed spray of water. The apparatus of the '442 patent utilizes a plurality of ice crystal generators located along the periphery of a blower to seed the air stream proximate the apparatus. This apparatus produces snow of moderate quality but requires a delicate control of the compressor utilized to generate the pulsed water flow and further necessitates the use of filtered water if problems of clogging are to be avoided.
U.S. Pat. No. 4,493,457 discloses the use of a blower having water spray nozzles arrayed around portions of its perimeter so as to spray water into the center of the air stream from points which are substantially above and substantially below that stream. This apparatus further includes a venturi-type seeder disposed within the center of the air stream so as to nucleate the spray at that point. U.S. Pat. No. 4,573,636 discloses an apparatus which is substantially similar to that of the '457 patent except that it further includes an air directing shroud disposed about the blower housing so as to further remove the spray nozzles from the air stream. Apparatus of this type produce relatively fine grained nuclei and are relatively difficult to keep tuned for optimum performance as atmospheric conditions change. Typically the spray nozzles must be changed as the temperature falls below 20.degree. F. if optimum quality snow and maximum efficiency are to be maintained.
U.S Pat. Nos. 4,105,161 and 4,222,519 describe a blower-type method and apparatus for snowmaking. As disclosed therein, the stream of air from the blower is deflected upward by a deflector plate. A nucleator is mounted in the shadow of the plate and adapted to project nuclei into the air stream from a point outside that stream. Additionally, a bank of nozzles is mounted above the air stream encircling only approximately the upper fourth thereof. These nozzles direct the spray of water into the air stream from a point outside that stream. This apparatus also requires precise control of operational parameters to assure maximum efficiency.
All of the foregoing apparatus nucleate their water spray proximate the apparatus. In such an arrangement, dripping can frequently occur because the water spray is not finely dispersed, nor has it had a chance to cool since its introduction. It should be appreciated in the foregoing then that there is a need for snow-making apparatus method capable of delivering high volumes of quality snow at economical costs, without producing any dripping. Additionally, such apparatus should be simple to operate over a range of varying climatic conditions without the necessity for repeated readjustments. Such apparatus should also not be prone to freeze up or other weather induced difficulties. The present invention provides such a method and apparatus.
As will be described in greater detail hereinbelow, the snow-making apparatus of the present invention includes water spray nozzles and a nucleator which are both disposed within a high volume air stream so as to obtain maximum dispersion and cooling of water before contact with the nuclei. The present invention thus is adapted to efficiently manufacture and widely disperse high volumes of high quality snow under a variety of climatic conditions. Furthermore, the nucleator and nozzles of the apparatus are designed so as to prevent freezing of water therein.
As will be described in greater detail herein below, the nucleator of the present invention is capable of producing nuclei approximately four times larger in size than those produced by previously available equipment. As a consequence of the larger and more efficient nucleation, the present apparatus produces snow having superior qualities. Snow produced in accord with the present invention has a granular structure which is resistant to melting and wearing and well adapted to promote drainage of melt-water therethrough. The granular structure of the snow prevents compaction permitting ready grooming of the snow into a high quality surface for skiing. These and other advantages of the present invention will be readily apparent from the drawings, descriptions and claims which follow.